1. Field of the Invention
The present invention is in the field of transmucosal drug delivery devices, particularly in the field of transmucosal patches for use in isolating and maintaining a drug or other active ingredient against a mucosal surface in order to promote diffusion of the drug or other active agent therethrough, and more particularly in the field of backing layers for transmucosal patches.
2. Relevant Technology
Transmucosal drug delivery is an alternative method of systemic drug delivery. It offers several advantages over both injectable and enteral delivery. Drugs absorbed via the mucous membrane (e.g., oral, anal or vaginal mucosa) avoid the low pH gastric fluid and proteases, as well as first-pass metabolism in the liver. The onset of action is faster than oral administration. Unlike injections, transmucosal delivery is non-invasive and not painful. Moreover, a patient can administer the medicine without help from a medical professional.
There is considerable interest in developing new dosage forms that can deliver drugs and other active agents across the mucosa of humans and mammals. In general, oral and other transmucosal dosage forms can be classified in one of three categories: (1) solid forms, (2) gum, and (3) patches. Examples of common solid dosage forms include lozenges, lozenges having a handle (e.g., lollipops), buccal tablets, and sublingual tablets. As the solid matrix dissolves in the oral cavity it releases the drug, which is absorbed by the oral mucosa. This type of dosage form is referred to as an “open system” because saliva can flow freely to and from the dosage form to dissolve the formulation. Drug concentration is generally controlled by how fast the matrix is dissolved, which is controlled by how fast the patient sucks the unit.
Gum, like lozenges and tablets, is an open system. When this dosage form is chewed the drug is released from gum into the oral cavity where it can be absorbed by oral mucosa. Drug release from gum is controlled by the make up of the delivery device, as well as how fast the gum is chewed. In general, gum dosage forms last longer than lozenges or tablets.
The term “buccal patch” typically refers to a flexible film that adheres to the oral mucosa and delivers a drug over a period of time. The buccal patch dosage form can be further divided into three types or subcategories: (1) dissolvable matrix patches, (2) patches having a non-dissolvable backing, and (3) patches with a dissolvable backing.
For examples known in the art of buccal patch technology see U.S. Pat. No. 3,598,122; U.S. Pat. No. 3,972,995; U.S. Pat. No. 4,517,173; U.S. Pat. No. 4,573,996; U.S. Pat. No. 4,572,832; U.S. Pat. No. 4,704,119; U.S. Pat. No. 4,713,243; U.S. Pat. No. 4,715,369; U.S. Pat. No. 4,740,365; U.S. Pat. No. 4,855,142; U.S. Pat. No. 4,876,092; U.S. Pat. No. 4,900,552; U.S. Pat. No. 4,900,554; U.S. Pat. No. 5,137,729; U.S. Pat. No. 5,298,256; U.S. Pat. No. 5,346,701; U.S. Pat. No. 5,516,523; U.S. Pat. No. 5,578,315; U.S. Pat. No. 5,599,554; U.S. Pat. No. 5,639,469; U.S. Pat. No. 5,766,620; U.S. Pat. No. 5,800,832; U.S. Pat. No. 5,863,555; U.S. Pat. No. 5,900,247; U.S. Pat. No. 6,159,498; U.S. Pat. No. 6,210,699; and U.S. Pat. No. 6,319,510.
Dissolvable matrix patches work similar to gum, lozenge and tablet dosage forms. The dissolving matrix releases the drug into the oral cavity for absorption by oral mucosa. They usually last longer than lozenges or tablets. Unlike gum, dissolvable matrix patches release the drug passively rather than actively. One limitation of all these systems is that the drug concentration in the mouth is not well controlled. In order to control the drug concentration over the period of drug delivery, buccal patches with backings were developed. Controlling drug concentration is particularly important when mucosally delivering drugs that require the help of permeation enhancers. Permeation enhancers are chemicals that can temporarily compromise the integrity of the oral mucosa so that drug delivery can be enhanced. The concentration of enhancers needs to be carefully controlled. If the concentration is too high, the enhancer can cause mucosal irritation or damage. If too low, it may not provide the desired enhancement of drug delivery. One way to maintain control of both drug and enhancer concentration is to include a backing so that the active formulation of the buccal patch is completely isolated from the surrounding environment, especially the saliva of the oral cavity.
There are two types of backing systems in the buccal patch dosage form: dissolvable and non-dissolvable. Non-dissolvable backings are usually flexible. They are designed to stay in the oral cavity for long periods of time, e.g., up to 10-15 hours. The disadvantage is that the patch has to be removed from oral mucosa by the patient after drug administration.
Patches with dissolvable backings are designed to stay in the oral cavity for a short period of time. The backing controls the local environment inside the patch so that high efficient drug delivery can be achieved in a controlled fashion. Over time, the backing dissolves or disintegrates in the oral cavity (e.g., when exposed to saliva) in order for all or part of the delivery device to go away. Such devices eliminate the need to remove the patch after treatment has been completed.
One of the challenges of providing patches with a dissolvable and/or disintegratable backing has been the need to provide materials that are able to provide an adequate barrier, in order to control the drug and/or permeation enhancer concentration over the period of drug delivery, while still being able to dissolve and/or disintegrate over time. There is an ongoing need to develop improved backing layers for use with transmucosal delivery devices, especially oral transmucosal delivery devices, that are able to dissolve and/or disintegrate over time when exposed to moisture; and that also provide sufficient barrier properties so as to prevent, or at least partially inhibit or slow, the tendency of drugs or other active agents from diffusing through the backing layer. The present invention overcomes shortcomings of prior art devices.